Today: Water Stress and Genetically Modifying Plants

Fig Water moves from the ground through roots into the shoot and out stomata in the leaves.

What happened to this root?

Flooding, constant submersion… Why would the plant respond like this?

Stomata control entry of CO 2 and exit of H 2 O from plant leaves Stomata Fig 30.10

What about when water is scarce?

Fig Structural adaptations of a plant that grows in an arid environment Oleander

Structural adaptations of a plant that grows in an arid environment: Thick cuticle Thick epidermis Recessed stomata Oleander Fig 37.16

Stomata density can change depending on the environment. Typically ~ /mm 2

Individual plants can change stomata number to adjust for changes in the environment. Only mature leaves exposed to high CO 2 New leaves develop with fewer stomata JA Lake et al (10 May 2001) Nature 411, 154

Measurements of herbarium samples and present day samples have shown a 40% decrease in stomata over the last 200 years. F. I. Woodward (18 June 1987) Nature 327,

Changes in precipitation

Irrigating crops eventually leads to increased soil salinity

Freshwater is not pure water. It contains many salts, such as: sodium 6mg/L; chloride 7mg/L; calcium 15mg/L; sulfate 11mg/L; silica 7mg/L; magnesium 4mg/L; and potassium 3mg/L

Human resource production and use

Worldwide Grain Production per Person

Land use in USA, 1997

from TeosinteMaize By artificial selection that began ~10,000 years ago.

Hunter- Gatherer Agricultural Industrial

Genetic Engineering: Direct manipulation of DNA

We can now insert new genes or modify existing genes of plants

Agrobacterium infect plants, inserting some of their DNA into the plants genome. Fig 19.17

Agrobacterium infect plants, inserting some of their DNA into the plants genome.

Fig After inserting a gene into the Agrobacteria, they will insert that gene into the plant's DNA.

Millions of Hectares Texas = 70 ha Global area planted with GM crops

The agricultural release of genetically modified organisms is the largest scale experiment that has ever been performed.

Why Change a Plant’s DNA? Can change plant so that it has new or different characteristics –Insect resistance (Bt toxin) –Herbicide resistance (Round-up) –Drought or other stress resistance Tbl 19.5

% of Total US Acres Common GM Crops in the U.S. ce/2007/09/mon santo-is- hap.html

Are Genetically Modifying Plants Safe?

Human impacts: Dead zone in Gulf of Mexico from Mississippi River es- picayune/2007/06/despit e_promises_to_fix_it_th e.html

Pollen is easily transferred from plant to plant, and to related species.

GM crops illegal GM crops found in Oaxaca and other MX states Genetic information moves.

GM crops illegal GM crops found in Oaxaca and other MX states Genetic information moves, and is self-replicating.

Monsanto's is one of the largest sellers of GMO's Monsanto Stock price

Next: Animals